1. Field of the Invention
This invention relates in general to the field of medical implants and more particularly to a stent which is constructed in an improved manner for simple and effective placement in a body passage to reinforce a damaged area.
In another aspect of the invention, stent assemblies are provided which include sensing devices such as blood glucose sensors.
2. Description of the Prior Art
Tubular prostheses commonly known as stents have been used to reinforce and strengthen damaged blood vessels and other body passages. For example, the blood vessels can collapse, dilate, become partially occluded or otherwise damaged by disease or other causes. The presence of an aneurysm or stricture in the blood vessel often requires implantation of a stent to strengthen the vascular wall in the area of the damage. Other passages in the body can also sometimes benefit from stent implantation, including the esophagus, the trachea, the gastro intestinal tract, the bile duct, the ureter and the urethra.
The benefits of self-expanding stents have been recognized. A self-expanding stent is held in a contracted state until it has been positioned properly, typically with the aid of an instrument such as a catheter. After the stent has been placed properly in the damaged blood vessel, it is allowed to expand against the damaged vessel wall in order to reinforce the damaged area. Examples of self-expanding stents are disclosed in U.S. Pat. Nos. 5,026,377 and 5,078,720 to Burton et al., U.S. Pat. No. 5,019,085 to Hillstead, U.S. Pat. No. 4,969,458 to Wiktor, and U.S. Pat. No. 5,041,126 to Gianturco. The Wicktor and Gianturco stents are in the form of coiled or looped wires that are unable to contact the entirety of the weakened vessel wall. The same is true of the Hillstead stent which takes the form of a multiple loop wire structure. The stents disclosed in the two Burton patents are braided structures that are likewise incapable of contacting the entirety of the damaged vessel wall. All of the stents and particularly their placement means are complicated to construct, and the stents are difficult to place precisely in the damaged vessel.
A number of attempts have been made in the past to develop in vivo sensors for continuously monitoring various conditions. To give but one example, a large number of glucose sensors have been proposed in the past for use by diabetic patients. Such sensors are designed to continuously monitor glucose levels in the blood. Prior devices of this character have been plagued by a number of deficiencies, most notably inaccuracies and the inability for invasive sensors to remain in place over long periods of time.